1. Technical Field
This invention relates generally to semiconductor device manufacturing, and in particular the manufacture of metal oxide semiconductor field effect transistor (MOSFET) structures. More particularly, the invention relates to methods of making MOSFETs that apply gate stress engineering principles.
2. Background Art
With the aggressive scaling of complimentary metal oxide semiconductor (CMOS) technologies, stress engineering is becoming more important to improve device performance. The application of stresses to channels of field effect transistors (FETs) is known to improve their performance. When applied in a longitudinal direction (i.e., in the direction of current flow), tensile stress is known to enhance electron mobility (or n-channel FET (nFET) drive currents) while compressive stress is known to enhance hole mobility (or p-channel FET (PFET) drive currents).
The source of stress can be inserted from multiple elements in a MOSFET, such as the shallow trench isolation (STI), embedded source/drain stressors, a stressed substrate, or an additional nitride capping layer. In view of the foregoing, there is a need in the art for an improvement to the related art.